Recently, the shortage of ingestion of calcium is often pointed out and this phenomenon is notable in growing children and aged persons. In order to solve the shortage of calcium ingestion, calcium-enriched foods have come to be sold. Even in cow's milk which is generally said to have a high content of calcium, it has been attempted to sell a calcium-enriched cow's milk by further adding calcium. Further, other calcium-enriched products such as juice and milk powder, instant noodles, biscuits, etc., are started to be sold.
For example, in cow's milk and yogurt, a water-soluble inorganic acid form or organic acid form calcium such as calcium lactate and calcium chloride, a water-difficultly soluble inorganic form calcium such as calcium carbonate and calcium phosphate are used.
However, the water-soluble inorganic acid form or organic acid form calcium are liable to damage the stability of proteins contained in cow's milk and yogurt and thus they have a disadvantage that it is difficult to add more than a given level to thus prevent a large amount of use as materials of calcium.
On the other hand, the water-insoluble calcium in an inorganic form does not damage the stability of proteins contained in cow's milk and yogurt due to water-insolubility and thus it can be used in a large amount. The calcium in an inorganic form generally has, however, a high specific gravity of 2.7 or more and thus when said calcium is dispersed in cow's milk, it precipitates in a short time to undesirably lower the beauty in appearance. As a result, it has a disadvantage that it can not be used in a large amount.
Many methods for adding a large amount of calcium to foods have been heretofore proposed. For example, as a method for preparing a slurry of a calcium agent in an inorganic form, Japanese Patent Non-examined publication (Kokai) No. 64-69513 proposes a method for improving dispersibility of calcium carbonate by irradiating supersonic wave to a calcium carbonate slurry which was not subjected to drying and pulverization in the production step or to a mixture of the calcium carbonate slurry and a hydrophilic emulsifier with an HLB of not less than 10.
In Example 2 of this publication, a preparation method of a calcium agent slurry having approximately 8% by weight of a solid content of calcium carbonate by irradiating supersonic wave to a mixture of a 10% by weight of calcium carbonate slurry and an aqueous solution of approximately 6% by weight of sucrose fatty acid ester of the HLB 15.
However, with such a low concentrated calcium carbonate of 8% by weight or so obtained by this method, though a calcium agent having a good dispersibility can be obtained, it is difficult to prepare a calcium agent slurry having an average particle size of less than 0.3 μm which is excellent in dispersibility and applicable to foods being stored for a long period of time such as long-life cow's milk, and even when prepared, energy cost required for dispersion unavoidably increases. Moreover, not only an increase in energy cost, but circulation costs such as containers of the calcium agent slurry, cold storage equipment, cold storage, and transportation increase and thus it is not a preferable method.
Further, Japanese Patent Non-examined Publication (Kokai) No. 6-127909 discloses a method for preparing a calcium phosphate dispersion by wet-pulverizing a mixture of a sucrose stearic acid ester with the HLB 16 and calcium phosphate under the specific conditions, and Japanese Patent Non-examined Publication (Kokai) No. 6-127939 discloses a method for preparing a calcium carbonate dispersion by wet-pulverizing a mixture of a sucrose stearic acid ester with the HLB 16 and calcium carbonate in the similar manner.
According to these methods, though it is possible to prepare a calcium agent slurry of an average particle size of less than 0.3 μm having a good dispersibility, the solid concentration of a calcium agent slurry proposed is only approximately 10% by weight at highest, and are also included the problems associated with equipment cost and circulation cost, as in the case of the method proposed by the above-mentioned Japanese Patent Non-examined Publication (Kokai) No. 64-69513.
Moreover, Japanese Patent Non-examined Publication (Kokai) No. 9-9919 proposes a method for improving dispersibility by adding to calcium carbonate at least one selected from the group consisting of phospholipid and protein decomposition products, followed by wet-pulverizing. However, the product obtained by this method includes the problems in flavor such as odor and bitterness. Moreover, according to this publication, since the calcium dispersion liquid obtained contains calcium carbonate of an average particle size of 1 to 3 μm, a cow's milk added with calcium obtained by this method is poor in recovery of calcium carbonate in a centrifugal separator such as a clarifier used in the production step, the precipitation tends to take place in foods such as cow's milk and thus it is not suited for foods being stored for a long period of time such as long-life cow's milk.
Furthermore, Japanese Patent Non-examined Publication (Kokai) No. 6-197736 proposes a method for preparing a dried powder by drying by the use of a drying machine such as a spray dryer a calcium agent slurry comprising a mixture of a sucrose stearic acid ester with the HLB 16 and calcium phosphate or calcium carbonate. However, the solid concentration of a calcium agent of a calcium agent slurry as the material to be dried is as low as approximately 10% by weight and thus there are also included the problems to be improved from the viewpoint of a drying energy cost and an investment cost in a drying equipment.
Moreover, WO 98-42210 proposes a highly concentrated food additive slurry composition and/or powder composition which comprises mixing at least one selected from calcium carbonate, calcium phosphate and ferric pyrophosphate, and gum arabic, and further a food composition containing the same. However, the gum arabic used in this method is a natural product and thus its cost had extremely increased, in the past, due to the reduced production caused by a natural disaster. In addition, since it is an imported product, it is often difficult to obtain by an influence of the world situation. Accordingly, there was a problem in respect of a stable supply of cheap products.
In recent years, with a development of containers being stored for a long period of time for cow's milk, yogurt, juice or the like and a storage method therefor, cases where those foods are stored for a long period of time in shops, automatic vending machines, large-size domestic iceboxes or the like are increasing. In such cases, when calcium carbonate particles added for the calcium-enrichment of those foods are not good in dispersibility in the foods, they precipitate at the bottom of the container during the storage for a long period of time, which often gives unpleasant and unclean feel and impression to drinkers who take liquid foods such as cow's milk and juice.
Accordingly, in liquid foods added with inorganic particles such as calcium carbonate prepared at present for the calcium-enrichment and put on the market, since the period of dispersion stability in foods is short, the amount of the inorganic particles added have to be limited to an extremely small amount. Otherwise, the use of the inorganic particles has to be limited to such liquid foods as taken within 1 to 2 days after being purchased by consumers.
Further, in the recent noodles industry, especially instant noodles industry, a variety of products added with various minerals and vitamins are developed from the need of differentiation, gastronome (gourmet) tendency and the like. Though calcium carbonate added to enrich calcium has to be dispersed uniformly in the noodles, if dispersibility and fluidity of the calcium are not sufficient, the calcium content in the noodles becomes uneven and that is not suited for a calcium-enriched food. Moreover, in order to solve the above problem, it is necessary to stir materials of noodles and calcium carbonate for a long time or vigorously to mix them uniformly and this is also undesirable from the viewpoint of energy cost.
Furthermore, in recent years the activity of magnesium in a living body is drawing attention. Magnesium is closely related with metabolism of calcium, and its shortage causes various symptoms due to dysbolism. Further, magnesium is related to various enzymatic reactions, and is said to maintain the homeostasis in the body. However, since the majority of magnesium is lost in the food refining process, it tends to be lacking in the eating life of the present days, and therefore, magnesium-enriched food is attracting attention lately.
For example, in soft drinks a water-soluble magnesium such as magnesium chloride and magnesium sulfate, and a water-insoluble or water-difficultly soluble inorganic form magnesium such as magnesium oxide are added for the purpose of enriching magnesium. However, the water-soluble organic or inorganic form magnesium is strong in bitterness and thus it can not be denied that its amount added is limited in respect of taste. Moreover, when the water-insoluble or water-difficultly soluble inorganic form magnesium such as magnesium oxide is used, it has a specific gravity as high as 3.0 or more. Accordingly, if it is dispersed in, for example, soft drinks, it precipitates in a short time to undesirably lower the eating impression and the beauty in appearance. As a result, it has a disadvantage that it can not be used in a large amount, as in the water-soluble magnesium.
In light of the foregoing situation, the present invention is to provide a food additive slurry composition or powder composition having a high concentration which enhances circulation economy and having a high dispersibility which is suitable as an additive for foods such as cow's milk and instant noodles, and a food composition containing the same.